The invention relates to a method and apparatus for removing a bicycle chain sprocket from a bicycle sprocket cluster, as found in conventional multi-speed pedal bicycles utilizing derailleur gear changers.
In modern, multi-speed pedal bicycles, a main drive chain is shifted by a derailleur gear shifter to engage and disengage bicycle chain sprockets of a sprocket cluster usually having at least five sprockets spaced laterally apart. The sprockets are mounted on a freewheel body, the body having a fixed inner portion secured to the wheel hub, and a freewheeling outer portion to which the sprockets are secured. Commonly, the larger or inner sprockets are splined or otherwise non-rotatably mounted on the outer portion, and the smaller one, two, and/or three outermost sprockets are threaded onto the outer portion with right hand threads, which also prevent the inner sprockets from coming from the body. During normal operation of the bicycle, the smaller outermost sprocket is tightened on its threaded connection to the outer portion, making removal difficult. To remove the threaded outermost sprocket, the sprocket must be rotated anti-clockwise relative to the outer portion of the freewheel body. Normally the sprocket itself can be rotated by a "chain whip" which is a lever arm and a short length of chain adapted to engage teeth of the sprocket. In order to prevent the outer portion of the freewheel body rotating freely due to the freewheel rachet mechanism, a freewheel vice or a second chain whip is used to engage the outer portion and prevent this rotation. Chain hips, and particularly vices, are relatively heavy tools and are not usually considered portable on bicycles. Consequently, roadside replacement of sprockets usually is not considered practical with prior art devices. Furthermore, chain whips and freewheel vices are relatively expensive items carried only by bicycle service outlets, and thus it is not usual for a bicycle owner to contemplate removing and replacing sprockets from a freewheel himself.